/*
 *  Copyright 2013 The WebRTC Project Authors. All rights reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

package org.appspot.apprtc;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.util.Log;
import android.util.TypedValue;
import android.widget.ScrollView;
import android.widget.TextView;

import java.io.PrintWriter;
import java.io.StringWriter;

/**
 * Singleton helper: install a default unhandled exception handler which shows
 * an informative dialog and kills the app.  Useful for apps whose
 * error-handling consists of throwing RuntimeExceptions.
 * NOTE: almost always more useful to
 * Thread.setDefaultUncaughtExceptionHandler() rather than
 * Thread.setUncaughtExceptionHandler(), to apply to background threads as well.
 */
public class UnhandledExceptionHandler implements Thread.UncaughtExceptionHandler {
	private static final String TAG = "AppRTCMobileActivity";
	private final Activity activity;

	public UnhandledExceptionHandler(final Activity activity) {
		this.activity = activity;
	}

	@Override
	public void uncaughtException(Thread unusedThread, final Throwable e) {
		activity.runOnUiThread(new Runnable() {
			@Override
			public void run() {
				String title = "Fatal error: " + getTopLevelCauseMessage(e);
				String msg = getRecursiveStackTrace(e);
				TextView errorView = new TextView(activity);
				errorView.setText(msg);
				errorView.setTextSize(TypedValue.COMPLEX_UNIT_SP, 8);
				ScrollView scrollingContainer = new ScrollView(activity);
				scrollingContainer.addView(errorView);
				Log.e(TAG, title + "\n\n" + msg);
				DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener() {
					@Override
					public void onClick(DialogInterface dialog, int which) {
						dialog.dismiss();
						System.exit(1);
					}
				};
				AlertDialog.Builder builder = new AlertDialog.Builder(activity);
				builder.setTitle(title)
						.setView(scrollingContainer)
						.setPositiveButton("Exit", listener)
						.show();
			}
		});
	}

	// Returns the Message attached to the original Cause of |t|.
	private static String getTopLevelCauseMessage(Throwable t) {
		Throwable topLevelCause = t;
		while (topLevelCause.getCause() != null) {
			topLevelCause = topLevelCause.getCause();
		}
		return topLevelCause.getMessage();
	}

	// Returns a human-readable String of the stacktrace in |t|, recursively
	// through all Causes that led to |t|.
	private static String getRecursiveStackTrace(Throwable t) {
		StringWriter writer = new StringWriter();
		t.printStackTrace(new PrintWriter(writer));
		return writer.toString();
	}
}
